1. Field of the Invention
The present invention relates to a liquid treatment method and apparatus for washing an object to be processed, such as a semiconductor wafer or glass substrate for an LCD, with a washing liquid after the object to be processed has been treated with chemicals.
2. Description of Related Art
Liquid treatment methods that are widely used during the fabrication of semiconductor devices generally involve immersing objects to be processed, such as semiconductor wafers or glass substrates for LCDs (hereinafter referred to simply as "wafers"), in a sequence of baths filled with liquids such as chemicals or a washing liquid, to treat them and wash them.
The washing method described below is one known example of these liquid treatment methods. With this washing method, it is known to accommodate objects to be processed such as semiconductor wafers (hereinafter called "wafers") within a treatment bath while they are held in a holder means such as a wafer boat, and a processing liquid such as ammonia, hydrochloric acid, or hydrofluoric acid is supplied to the wafers in a jet from means such as a chemical supply nozzle. A circulating supply is set up, in other words, liquid is allowed to overflow from the treatment bath into the outer bath and is then circulated back from the outer bath into the treatment bath. After processing to remove contaminants such as particles or metal ions adhering to the wafers or remove oxide films therefrom, the chemicals are discharged. A washing liquid such as pure water is then supplied in a jet towards the wafers from a washing liquid supply nozzle, and water is also allowed to overflow from the treatment bath into the outer bath as the wafers are washed.
In this prior-art type of liquid treatment method, it often happens that the chemicals used in the chemical treatment will remain in the chemical supply nozzle after the chemicals have been discharged. There is a danger that such residual chemicals will subsequently dry to form particles that adhere to the wafers, or further problems could occur if they lower the resistivity of the pure water used during the washing after the treatment, causing a lowering of the washing efficiency.
This type of liquid treatment method has a further problem in that the necessity of providing two types of supply nozzle (the chemical supply nozzle and the washing liquid supply nozzle) plus the corresponding piping and attachment devices leads to an increase in size of the apparatus and complicates the installation.